Tert-amine treatment

ABSTRACT

A tert-amine which contains an acid-activated color body precursor is treated to prevent it or a derivative thereof, e.g., an amine oxide, betaine, or quaternary ammonium compound, from turning pink when exposed to acidic conditions by contacting it with an amido compound containing a --CO.NH-- group.

FIELD OF INVENTION

This invention relates to a process for treating a tert-amine to preventpink coloration of the amine or a derivative thereof when exposed toacidic conditions.

BACKGROUND

As disclosed in U.S. Pat. No. 4,347,381 (Tuvell), it is known that sometert-amines and derivatives thereof, e.g., amine oxides, betaines, andquaternary ammonium compounds, are subject to turning pink when exposedto acidic conditions. Neither the pink color body that is formed underacidic conditions nor its acid-activated precursor has yet beenidentified, and it is not known if the presence of the color bodyprecursor as an impurity in some tert-amines is attributable to the rawmaterials and/or the techniques used in their syntheses. However,regardless of the primary reason for the discoloration, the pinkcoloration of the amines and their derivatives is undesirable because ofits interference with dyes which are apt to be included in theformulations in which they are used.

A pink tert-amine or derivative thereof can have its color reduced inintensity or even removed by treating it with a bleaching agent, such ashydrogen peroxide, sodium sulfite, sodium bisulfite, sodium thiosulfate,or sodium hypochlorite, as in Tuvell; but it would be preferable toprevent the discoloration from occurring rather than to remove or reducethe discoloration later.

U.S. Pat. No. 3,922,306 (Takaku et al.) teaches that this discolorationof amine salts can sometimes be prevented when the amines are reactedwith 0.01-5% by weight of certain borohydrides. According to Takaku etal., the effectiveness of the borohydrides in this regard is unexpectedand unique, since it cannot be attained by the use of other reducingagents, such as the sodium sulfite or bisulfite, hydrazine, orhypophosphorous acid of their comparative example. However, it would bedesirable to find an alternative to the borohydrides as agents forpreventing discoloration of tert-amines and derivatives. As indicated byTuvell, the borohydrides are too expensive to make their usecommercially attractive.

SUMMARY OF INVENTION

It has been discovered that a tert-amine which contains anacid-activated color body precursor can be treated to prevent it or aderivative thereof from turning pink when exposed to acidic conditionsby contacting it with an amido compound which contains a --CO.NH--group.

DETAILED DESCRIPTION

As is known, the tert-amines which present the aforementioneddiscoloration problem are amines which contain at least one long-chainalkyl group, and any of these tert-amines can be treated in accordancewith the present invention. However, because of their use in preparingderivatives having the greatest commercial interest, the tert-amineswhich are treated are preferably compounds corresponding to the formulaRR'R"N in which R is an alkyl group containing 8-22 carbons; R' is amethyl, ethyl, or hydroxyethyl group; and R" is independently selectedfrom methyl, ethyl, hydroxyethyl, and alkyl groups containing 8-22carbons.

Of the tert-amines in which R' and R" are independently selected frommethyl, ethyl, and hydroxyethyl, those which are of greatest interestare generally the tert-amines in which both R' and R" are methyl; and itis usually also preferred for R' to be methyl in the tert-amines whereinR and R" are independently selected from alkyl groups containing 8-22carbons.

Exemplary of these tert-amines are N-octyldiethylamine,N-octyl-N-hydroxyethylmethylamine, N,N-didecylmethylamine,N-dodecyl-N-tetradecylhydroxyethylamine, N,N-ditetradecylmethylamine,N-tetradecyldimethylamine, N-hexadecyl-N-ethylmethylamine,N-octadecyl-N-eicosylmethylamine, N-docosyldimethylamine,N-tetracosyldimethylamine, and the like.

The amido compound with which the tert-amine is contacted can be anyorganic compound containing a --CO.NH-- group, such as an amide derivedfrom an alkanoic or benzoic acid, an anilide or other N-monosubstitutedderivative of such an amide, a heterocyclic amide, urea, or an alkylcarbamate. Exemplary of such compounds are formamide, acetamide,butyramide, palmitamide, stearamide, benzamide, N-methylformamide,N-ethylacetamide, acetanilide, benzanilide, 2-pyrrolidone, urea, and thealkyl carbamates in which the alkyl group is methyl, ethyl, propyl,isopropyl, butyl, hexyl, decyl, tetradecyl, or other alkyl groupcontaining 1-20 carbons.

The amount of amido compound employed is generally at least about 0.1%,based on the weight of the tert-amine, although lesser amounts areeffective in at least reducing the discoloration that occurs underacidic conditions and thus can be usefully employed if desired. Sincetreatment with about 0.1% by weight of the amido compound is usuallysufficient to prevent the tert-amine or a derivative thereof fromturning pink when exposed to acidic conditions, it is seldom necessaryto use a larger amount; but larger amounts can be utilized withoutdeleterious effect. Thus, in most cases, the tert-amine is contactedwith about 0.05-5%, preferably about 0.1-1%, most preferably about0.1-0.5% of the amido compound, based on the weight of the tert-amine.

The treatment of the tert-amine with the amido compound is believed toresult in a reaction between the amido compound and the acid-activatedcolor body precursor and a consequent prevention of the formation of acolor body when the tert-amine or a derivative thereof is exposed toacidic conditions. This treatment is accomplished by contacting thetert-amine and amido compound in any suitable way, e.g., by dissolvingor slurrying the amido compound in the tert-amine, and then removing theamido compound, e.g., by distillation or filtration.

Although the effectiveness of the treatment in preventing laterdiscoloration of the tert-amine is probably at least virtuallyinstantaneous even at room temperature, it is generally desirable tomaintain contact between the tert-amine and amido compound for a shorttime, e.g., 1-30 minutes, to insure that effectiveness. Also, anelevated temperature could be used for the treatment without deleteriouseffect. However, it is preferred to conduct the treatment at ambienttemperatures.

The invention is advantageous as an economical means of treatingtert-amines so that neither they nor their derivatives, e.g., amineoxides, betaines, and quaternary ammonium compounds, will turn pink whenexposed to acidic conditions.

The following examples are given to illustrate the invention and are notintended as a limitation thereof. Unless otherwise specified, quantitiesmentioned in the example are quantities by weight.

EXAMPLE I Control

An aliquot of a distilled N-tetradecyldimethylamine was acidified withHCl. Below a pH of 6-7, it developed an intense pink color.

EXAMPLE II

A 1% solution of formamide in another aliquot of the distilledN-tetradecyldimethylamine was shaken at room temperature for 15 minutesand then distilled to remove the amide. When treated in this manner andthen acidified with HCl as in Example I, the amine remained colorless.

EXAMPLE III

Two experiments were performed by repeating Example II except forreplacing the formamide with 2-pyrrolidone and methyl carbamate,respectively. In both cases the treated amine remained colorless whenacidified.

EXAMPLE IV

A 1% slurry of urea in another aliquot of the distilledN-tetradecyldimethylamine was shaken at room temperature for 15 minutesand then filtered to remove the urea. When treated in this manner andthen acidified with HCl as in Example I, the amine remained colorless.

What is claimed is:
 1. A process for treating a tert-amine that containsan acid-activated color body precursor so as to prevent pink colorationof the tert-amine or a derivative thereof when exposed to acidicconditions, which process comprises contacting the tert-amine with anamido compound containing a --CO.NH-- group and selected from the groupconsisting of amides derived from alkanoic and benzoic acids andN-monosubstituted derivatives thereof, heterocyclic amides, urea, andalkyl carbamates.
 2. The process of claim 1 wherein the tert-amine is acompound corresponding to the formula RR'R"N in which R is an alkylgroup containing 8-22 carbons; R' is a methyl, ethyl, or hydroxyethylgroup; and R" is independently selected from methyl, ethyl,hydroxyethyl, and alkyl groups containing 8-22 carbons.
 3. The processof claim 2 wherein R" is methyl, ethyl, or hydroxyethyl.
 4. The processof claim 3 wherein R' and R" are methyl.
 5. The process of claim 2wherein R" is an alkyl group containing 8-22 carbons.
 6. The process ofclaim 5 wherein R' is methyl.
 7. A process for treating a tert-aminethat contains an acid-activated color body precursor so as to preventpink coloration of the tert-amine or a derivative thereof when exposedto acidic conditions, which process comprises contacting the tert-aminewith an amido compound selected from the group consisting of formamide,2-pyrrolidone, urea, and methyl carbamate.
 8. The process of claim 7wherein the amido compound is formamide.
 9. The process of claim 7wherein the amido compound is 2-pyrrolidone.
 10. The process of claim 7wherein the amido compound is urea.
 11. The process of claim 7 whereinthe amido compound is methyl carbamate.
 12. The process of claim 1wherein the amount of amido compound is at least about 0.1%, based onthe weight of the tert-amine.
 13. The process of claim 1 wherein thetert-amine is maintained in contact with the amido compound for 1-30minutes at ambient temperature.